The present invention concerns a method for manufacturing a plurality of electro-optical or photovoltaic cells having at least three substrates and two cavities filled with a liquid for example liquid crystals. More particularly, the invention concerns a collective manufacturing method for a batch of such cells wherein the step of dividing the batch into individual cells is facilitated.
Double liquid crystal cells are well known in the state of the art and are intended for example to form colour image display devices. Such a double cell, which is for example disclosed in the Patent Application No. WO 89/00300, includes three parallel substrates, two outer substrates and an intermediate substrate connected in pairs by means of two sealing frames. The faces of the intermediate substrate and respectively the outer substrates which are located facing each other carry a set of electrodes and the two cavities defined respectively between the intermediate substrate and the two outer substrates are filled with liquid crystals.
The manufacture of this type of cell is currently performed in accordance with two methods.
According to the first method, two batches of conventional cells are manufactured, i.e. with two substrates and one cavity, the cells of each batch including the desired liquid crystals. The two batches are divided into individual cells and the individual cells of one batch are assembled by bonding using a suitable adhesive material to the individual cells of the other batch.
In order to make each of these batches, two large plates of glass or synthetic material are prepared, a pattern of sets of electrodes and conductive paths are made on the opposite faces of these plates, sealing material is deposited on one of said plates and a filling opening for each cell of the batch is arranged therein, the sealing material extending around each set of electrodes. The two base plates are then assembled to form an assembly including several rows of open cells. This assembly is then divided into rectilinear strips by glass scribing and breaking techniques (see for example U.S. U.S. Pat. No. 4,224,093) or by sawing along parallel straight lines. Since each cell has a filling opening along one edge of the strip, the cells are then filled, and their openings are sealed, then the strip is divided into individual rectangular cells along straight lines which are perpendicular to the preceding straight lines.
A first drawback of this method lies in the fact that the double cell which results therefrom has four substrates and consequently a significant thickness. Another drawback is the increase in the parallax effect between the two layers of liquid crystals because of the double thickness of the intermediate substrate which is formed in this case by two bonded plates. This is thus evidently detrimental to the quality of the displayed image. Moreover, this method involves a large number of manipulations, which makes it laborious and more expensive.
According to the second method, cells with three substrates are manufactured one by one because of the impossibility of cutting the three substrates simultaneously by conventional scribing and sawing techniques. Each manufacturing step has thus to be performed individually on each cell, which makes the manufacture of such cells tedious and naturally more expensive than if it could be performed in batches.